KR20120126107A - Fluororesin sheet - Google Patents

Abstract

An object of the present invention is to provide a fluororesin sheet which is inexpensive and has a high compression ratio, and a method for producing the same.
In order to solve the said subject, the fluororesin sheet of this invention is for sheet formation containing (A) fluororesin, (B) filler (except perlite), (C) pearlite, and (D) processing aid Characterized in that it is prepared from the composition.

Description

Fluorine resin sheet {Fluororesin sheet}

The present invention relates to a fluororesin sheet.

The sheet processed into a sheet shape by filling a fluororesin with a filler is added to the chemical resistance and heat resistance of the fluororesin, and in addition to the inherent functions and characteristics of the filler, or by improving the creep resistance, which is a defect of the fluororesin. It is used a lot in sealing materials.

As such a sealing material, the applicant of this application discloses the manufacturing method of the fluororesin sheet containing a fluororesin, a filler, and a processing aid in Unexamined-Japanese-Patent No. 2007-253519 (patent document 1). Clay etc. are mentioned as this filler. By this manufacturing method, high recoverability and high airtightness are compatible, and the fluororesin sheet suitable for a gasket material can be obtained.

However, since this fluororesin sheet was easy to become a hard sheet with a small compression ratio, when using the sheet as a gasket or the like, a high body part pressure was required to obtain a predetermined sealing property. In addition, when the sheet was thus hard, there was room for further improvement because of poor workability such as punching the sheet with a gasket having a desired shape.

Japanese Patent Publication No. 2007-253519

The present invention has been made in view of the above problems, and an object thereof is to provide a fluororesin sheet having a high compression ratio, low cost, and good processability at low body pressure.

MEANS TO SOLVE THE PROBLEM As a result of earnestly researching in order to solve the said problem, the sheet produced from the composition containing a fluororesin, a filler (except perlite), a pearlite, and a processing aid is inexpensive, and the compression rate This large, low body part pressure results in a sealing property equivalent to or higher than that of a conventional product, and the punching workability from the sheet to a gasket having a desired shape or the like is also found to be good, thus completing the present invention. It came to the following.

The specific structure of this invention is shown below.

The fluorine resin sheet of this invention was manufactured from the composition for sheet formation containing (A) fluororesin, (B) filler (except pearlite), (C) pearlite, and (D) processing aid. do.

It is preferable that the quantity of (C) pearlite in the said composition is 4-20 weight part with respect to a total of 100 weight part of (A) fluororesin, (B) filler (except pearlite), and (C) pearlite.

In addition, when referring to a "filler" hereafter, it means what does not contain a pearlite.

It is preferable that the quantity of (D) processing aid in the said composition is 5-50 weight part with respect to a total of 100 weight part of (A) fluororesin, (B) filler (except perlite), and (C) pearlite.

In the fluororesin sheet of the present invention, a porous pearlite (C) and a filler (B) other than that, for example, clay are used in combination and can be manufactured at low cost.

The fluororesin sheet which is excellent in secondary workability, such as punching to a gasket shape etc., and which has a high compression ratio at low body part pressure, and uses it at low body part pressure, can be obtained.

Hereinafter, the present invention will be described in more detail.

≪Fluorine resin sheet≫

The fluorine resin sheet of this invention was manufactured from the composition for sheet formation containing (A) fluororesin, (B) filler (except pearlite), (C) pearlite, and (D) processing aid. do.

<(A) Fluorine Resin>

As said (A) fluororesin, tetrafluoroethylene resin (PTFE), modified PTFE, vinylidene fluoride resin (PVDF), tetrafluoroethylene-ethylene copolymer resin (ETFE), trifluoroethylene ethylene resin (PCTFE), tetrafluoroethylene Conventionally well-known fluororesins, such as -6 fluoro propylene ethylene copolymer resin (FEP) and tetrafluoro ethylene- perfluoroalkyl copolymer resin (PFA), can be used preferably. Among these, tetrafluoroethylene resin (PTFE) is preferable from the viewpoint of workability in performing extrusion molding, rolling, and the like, and PTFE of fine powder obtained by emulsion polymerization is particularly preferable. Since PTFE of fine powder has a property of fiberizing when a shearing force is applied, it is entangled with (B) filler, (C) pearlite, etc. in the process of stirring and mixing each component in the composition mentioned later, and the sheet formation process. Since a composition and / or a sheet can be obtained, a fluororesin sheet excellent in sealing property and mechanical strength can be obtained.

When using PTFE as said (A) fluororesin, fluorine resins other than PTFE mentioned above for said fluororesin are small amounts, for example, 10 weight% (total amount of fluorine resin shall be 100 weight%) or less. It may be included in quantity.

As said (A) fluororesin, a powdery thing may be used as it is, and the dispersion which disperse | distributed fluororesin fine particle in water may be used.

<(B) filler>

As said (B) filler, except for the following pearlite (C), According to the objective, Carbon-type fillers, such as graphite, carbon black, expanded graphite, activated carbon, a carbon nanotube; Inorganic fillers such as talc, mica, clay, calcium carbonate, magnesium oxide, silicon carbide, alumina and silica; Or powder of resin, such as PPS; Etc. are used. Moreover, you may use the fiber material of 10 mm or less of fiber lengths which become carbon fiber, aramid fiber, lock wool, etc. as (B) filler.

According to this invention, even when the filling rate of (A) fluorine resin is low and the filling rate of (B) filler is high, a fluororesin sheet with a large compression rate can be obtained. Preferably the weight ratio of said (A) fluororesin and said (B) filler (except pearlite) becomes like this. Preferably it is 1: 0.1-3, More preferably, it is 1: 0.1-2.

When (B) filler is contained in such quantity, the fluororesin sheet which fully exhibits the characteristic of a filler can be obtained.

<(C) pearlite>

The pearlite (C) is a foam of volcanic rock containing a lot of silicic acid (SiO ₂ ), the composition of which is silicic acid (SiO ₂ 70-80%), alumina (Al ₂ O ₃ 10-20%) and Na ₂ O, K ₂ O (total 0-10%). Examples of the volcanic rock include pearlite, obsidian, pine rock, and the like. In the present invention, foam of any of these rocks can be used, but the oil absorption rate is porous. Excellent pearlite is particularly preferred.

Such (C) pearlite is very lightweight, has excellent thermal insulation, is inexpensive and nonflammable. For this reason, it is suitable for use at high temperature and an inexpensive fluororesin sheet can be obtained.

Moreover, since (C) pearlite is excellent also in liquid absorption, it is thought that in this invention, the (D) processing aid in the composition for sheet formation can be absorbed. And when forming a sheet from the composition for sheet formation, when using the following method (I), it is thought that (D) processing aid will be impregnated and hold | maintained in many holes in a pearlite at the time of a rolling process. For this reason, at the time of a rolling process, the hole structure of a pearlite is hard to be crushed, and when the (D) processing aid is volatilized in the subsequent drying process, it is thought that the sheet | seat obtained will hold a space | gap (hole) in a pearlite. Therefore, in particular, it is considered that a fluororesin sheet having a high compressibility and having a suitable sealing property at a low body pressure can be obtained.

The amount of the above-mentioned (C) pearlite in the sheet-forming composition is a total of (A) fluororesin, (B) filler (except for pearlite) and (C) pearlite ((A) + (B) + (C) ) With respect to 100 parts by weight, preferably 4 to 20 parts by weight, more preferably 5 to 8 parts by weight.

Moreover, also in the fluororesin sheet of this invention obtained, the quantity of the pearlite (C) with respect to (A) + (B) + (C) = 100 weight part is the same as the above.

In addition, the average particle diameter (measured by a laser particle size distribution analyzer) of (C) pearlite becomes like this. Preferably it is 150 micrometers or less, More preferably, it is about 75-125 micrometers.

(C) Perlite is contained in such an amount, Furthermore, if the average particle diameter of the perlite (C) exists in the said range, a fluororesin sheet with a high compression rate can be obtained, maintaining high airtightness.

If the amount of (C) pearlite in the composition for sheet formation is 5-8 weight part with respect to a total of 100 weight part of (A) fluororesin, (B) filler (except pearlite), and (C) pearlite, In particular, a fluororesin sheet having a balance of characteristics such as low compression ratio, high sealing property, high tensile strength and low stress relaxation property can be obtained.

<(D) processing aid>

There is no restriction | limiting in particular as said (D) processing aid, A conventionally well-known processing aid, for example, a petroleum hydrocarbon solvent, alcohols, water, etc. can be used.

As a commercial item of a petroleum hydrocarbon solvent, For example, isoper C (hydrocarbon type organic solvent, fractionation distillation temperature: 97-104 degreeC) by ExxonMobil Co., Ltd., isoper G (hydrocarbon type organic solvent, fractional distillation temperature), for example. ： 158 to 175 ° C), and isoper M (hydrocarbon-based organic solvent, fractional distillation temperature: 218 to 253 ° C), an industrial solvent having features such as non-normal hexane, low benzene, low aroma solvent, etc., Japan Cactus solvent R5N etc. of energy manufacture are mentioned.

When the following method (I) is used at the time of manufacturing a fluororesin sheet, this (D) processing aid should just be an amount which a suitable amount exists of a processing aid after a rolling process, and is specifically, in the composition for sheet formation The amount of the (D) processing aid is preferably 5 to 50 parts by weight, more preferably to 100 parts by weight of the total of (A) fluorine resin, (B) filler (except for pearlite) and (C) pearlite. Preferably it is 10-40 weight part. When the (D) processing aid is used in such an amount, the raw materials can be blended and mixed and dispersed easily and uniformly, and the workability from the obtained composition to the sheet is excellent. In addition, when manufacturing a fluororesin sheet, when using the following method (I), it can fully swell a fluororesin at the initial stage of the rolling process mentioned later, and all the processing aids before the baking process mentioned later Is not volatilized, and the sheet after rolling containing an appropriate amount of processing aids can be obtained.

The composition for sheet formation consists essentially of said (A) fluororesin, (B) filler, (C) pearlite, and (D) processing aid.

In order to prepare the composition for sheet formation containing these components, each said component may be added into a container by dividing a plurality of circuits at once or in small quantities in arbitrary order, and may be stirred and mixed.

Although the said method of stirring and mixing is not specifically limited, (A) fluororesin, (B) filler, (C) pearlite, and (D) processing aid are mix | blended so that it may correspond to the composition of the fluororesin sheet to manufacture, What is necessary is just to stir and mix in arbitrary order. When stirring efficiency is bad, you may add a lot of processing aids, and you may remove an extra processing aid by filtration after completion | finish of stirring.

Moreover, as temperature at the time of stirring and mixing, temperature lower than the roll temperature in a rolling process is preferable so that a processing aid may not volatilize.

[Method for producing fluorine resin sheet]

The manufacturing method of the fluororesin sheet of the present invention is not particularly limited as long as the fluororesin sheet can be formed from the composition for forming a sheet, and a conventionally known method can be used. Preferably, the composition for forming the sheet is prepared. The obtained preform is rolled at a roll temperature of 40 ° C. to 80 ° C., then dried and fired (hereinafter also referred to as method (I)).

Below, this method (I) is shown concretely.

≪Method (I) ≫

Method (I) includes a preforming step, a rolling step, a drying step and a firing step in this order.

<Preliminary molding process>

In the preforming step, the sheet forming composition is extrusion molded to produce a preform (extruded molded product).

Although the shape of this preform is not specifically limited, A rod shape or a ribbon shape is preferable in consideration of the efficiency of subsequent sheet formation, the homogeneity of sheet properties, and the like.

In the manufacturing method of this invention, it is preferable to perform a preforming process under temperature lower than the roll temperature in a rolling process so that a processing aid may not volatilize.

<Rolling process>

In the rolling process following a preforming process, a preform is rolled and shape | molded in a sheet form through the rolling roll represented by a biaxial roll.

In the manufacturing method of this invention, this rolling process is performed by making roll temperature into 40-80 degreeC.

If roll temperature exists in the said range, the hardness of (A) fluororesin will fall somewhat and it will become easy to densify a fluororesin sheet | seat. In addition, all of the (D) processing aids do not volatilize completely.

When a rolling process is performed at temperature lower than 40 degreeC, it will become difficult to volatilize a processing aid. On the other hand, when rolling at the temperature exceeding 80 degreeC, the said (D) processing aid will volatilize excessively, and there exists a tendency which cannot form a filler containing fluorine resin sheet with a large compressibility. In addition, since the processing aid (D) is excessively volatilized, and the processing aid remaining at the initial stage of the rolling process decreases, the (A) fluorine resin cannot be sufficiently swelled and fiberized, and thus the strength of the resulting fluorine resin sheet Tends to fall. Moreover, when the (D) processing aid in a composition is rapidly vaporized, a swelling phenomenon arises and there exists a tendency for the airtightness of a fluororesin sheet also to fall.

Moreover, in the manufacturing method of this invention, it is also possible to include the process of rolling the rolled sheet prepared by the said rolling process further, ie, repeating a rolling process a plurality of times (for example, 3 to 50 times). In order to leave an appropriate amount of processing aids in the sheet after the rolling step, it is preferable to appropriately adjust the number of rolling. In addition, when repeating a rolling process, roll interval is narrowed every time rolling is repeated.

When forming the sheet by rolling the preform with a biaxial roll, for example, if the distance between the rolls is set to 0.5 to 20 mm, and the roll surface moving speed (sheet extrusion speed) is set to 5 to 50 mm / second, the preform is rolled. do.

<Drying process>

In the drying step, the rolled sheet is left at room temperature or heated at a temperature below the melting point of the fluororesin to remove the processing aid.

<Firing process>

In the firing step, the sheet after the drying step is heated at a temperature equal to or higher than the melting point of the fluororesin and sintered. The heating temperature is somewhat different depending on the type of fluorine resin, considering that the entire sheet needs to be uniformly baked and that fluorine-based harmful gas is generated at an excessively high temperature. Is suitable.

[Fluorine resin sheet]

The fluororesin sheet is not particularly limited as long as it is produced from the composition for forming a sheet, but is preferably a sheet produced by the method (I). The fluororesin sheet is inexpensive and has a high compression ratio. Specifically, the compression ratio is preferably 7% or more, more preferably 8% or more, and the upper limit thereof may be 15%, and the amount of leakage (airtightness, φ48 × φ67). The surface pressure of 19.6 MPa and the nitrogen gas withstand pressure of 0.98 MPa) for a test piece having a thickness of 1.5 mm is preferably 7.0 × 10 ⁻³ Pa · m ³ / s or less, more preferably 2.0 × 10 ⁻⁴ Pa · m 3 / s or less The lower limit may be 1.0 × 10 ⁻⁵ Pa · m 3 / s.

Such a fluororesin sheet of the present invention can be used for a gasket, and the gasket of the fluororesin sheet of the present invention can be used for a long time under high temperature (for example, 200 ° C or higher), and is sealed even at a low body pressure. High gaskets can be obtained.

The said gasket can be manufactured easily by cutting out (punching) the fluororesin sheet of this invention to a target shape. The filler-containing fluororesin sheet of the present invention is easily cut (punched) and has high handleability.

[Example]

Hereinafter, the production method of the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples in any way.

<Test Method>

The test piece was produced from the sheet of thickness 1.5mm, and airtightness was measured as follows.

Leakage (confidentiality);

A gasket test piece punched to a size of φ48 mm × φ67 mm was mounted between a steel flange of φ100 mm × 50 mm in height and a surface roughness Rmax = 12 μm, and the surface pressure 19.6 MPa (200 kgf / cm 2 G) was The load was loaded as much as possible. After nitrogen gas internal pressure 0.98 MPa (1.0 kgf / cm <2> G) was loaded from the pressure introduction through-hole provided in the flange to the inside diameter of a gasket, the pressure introduction piping was sealed and hold | maintained for 1 hour. The pressure change before and after holding was read by the pressure sensor, and the leakage amount was calculated | required from the pressure drop.

Stress relaxation ;

The stress relaxation rate at 100 degreeC and 200 degreeC was measured based on ASTM F38 B method.

Compression rate;

The compressibility was measured based on ASTM F36.

The tensile strength;

Tensile strength was measured based on JIS R3453.

Example 1

PTFE (CD-1, Asahi Glass Co., Ltd. product): 17.1 kg,

Fine powder clay (XN-D325, manufactured by Anmi Sulfur Nonmetallic Materials Co., Ltd.): 9.6 kg,

Pearlite (average particle size 100 micrometers, Qingdao Okju Chemical Co., Ltd. product): 1.7 kg,

Hydrocarbon-based organic solvent (Isofer G, ExxonMobil): 7.5 kg

The mixture was mixed at room temperature for 15 minutes with a kneader, then aged for 16 hours at room temperature (25 ° C) to prepare a composition for sheet formation.

This composition was extruded at room temperature (25 degreeC) with the extruder of 300 mm x 200 mm, and the preform was produced.

This preform was rolled by the biaxial roll on conditions of a roll diameter of 700 mm, a roll spacing of 20 mm, a roll speed of 6 m / min, and a roll temperature of 70 ° C. Immediately after this rolling, the obtained sheet was rolled again with a roll interval of 10 mm, and similarly, the obtained sheet was gradually narrowed to a roll interval of 8 mm, 6 mm, 4 mm, 2 mm, and 1.5 mm. It rolled 5 times and obtained the sheet | seat of thickness 1.5mm.

The sheet was left at room temperature (25 ° C) for 24 hours to remove the processing aid, and then calcined at 350 ° C in an electric furnace for 3 hours to obtain a fluororesin sheet.

The leakage amount (airtightness) of this fluororesin sheet was 2.1x10 <^-5> (also == 2.1E-05) Pa * m <3> / s and the compression rate was 9%.

[Example 2]

The fluororesin sheet was manufactured by the same method as Example 1 except having changed the compounding composition of the composition for sheet formation used in Example 1 as shown in Table 1 below, and changing the roll temperature to 80 degreeC.

The leakage amount (airtightness) of this fluororesin sheet was 1.1x10 <^-4> Pa * m <3> / s, and the compression ratio was 10%.

[Example 3]

The sheet forming composition used in Example 1 was changed as shown in Table 1, and extruded at a room temperature (25 ° C) with a ring-shaped spherical extruder having an outer diameter of 300 mm and an inner diameter of 260 mm to prepare a preform. A fluororesin sheet was manufactured in the same manner as in Example 1 except for the above.

The leakage amount (airtightness) of this fluororesin sheet was 6.2x10 <^-4> Pa * m <3> / s, and the compression ratio was 9%.

Example 4

A fluororesin sheet was manufactured in the same manner as in Example 3, except that the composition for forming a sheet used in Example 3 was changed as shown in Table 1.

The leakage amount (airtightness) of this fluororesin sheet was 5.3x10 <^-4> Pa * m <3> / s, and the compression ratio was 10%.

Comparative Example 1

A fluororesin sheet was manufactured in the same manner as in Example 1, except that the composition for forming a sheet used in Example 1 was changed as shown in Table 1.

The leakage amount (airtightness) of this fluororesin sheet was 1.1x10 <^-4> Pa * m <3> / s, and the compression ratio was 6%.

Comparative Example 2

A fluororesin sheet was manufactured in the same manner as in Example 1, except that the composition for forming a sheet used in Example 1 was changed as shown in Table 1.

The leakage amount (airtightness) of this fluororesin sheet was 1.1x10 <^-4> Pa * m <3> / s, and the compression ratio was 4%.

Claims (3)

A fluorine resin sheet produced from a composition for forming a sheet containing (A) a fluororesin, (B) a filler (except pearlite), (C) pearlite, and (D) a processing aid. The method of claim 1,
The amount of (C) pearlite in the composition is 4 to 20 parts by weight based on 100 parts by weight of the total of (A) fluorine resin, (B) filler (except pearlite) and (C) pearlite. Fluorine resin sheet. The method of claim 1,
The amount of the (D) processing aid in the composition is 5 to 50 parts by weight based on 100 parts by weight of the total of (A) fluorine resin, (B) filler (except perlite) and (C) pearlite. Fluorine resin sheet.